1. The Field of the Invention
This invention relates to an isometric testing apparatus used in physical therapy for performing isometric strength tests on individual muscles or joints of a patient. More particularly, the present invention is directed to an isometric testing system having a platform upon which the patient may stand; an adjustable and pivoting seat adjusting in and out of a test area and pivoting to orient the patient; an adjustable and pivoting load cell to properly position and orient the load cell; and a plurality of engaging devices detachably coupled to the load cell by quick-connect coupling.
2. The Background Art
Isometric assessment of muscular strength has been employed extensively in orthopedic, sports, rehabilitation, and industrial clinics for more than 40 years. Isometric testing typically involves a maximum voluntary contraction at a specified joint angle or functional position against an unyielding pad or handle connected to a force measuring device. In contrast to isometric testing, isokinetic testing measures strength throughout a range of motion of a body segment using a yielding, constant velocity device to which a force measuring device is attached. The isometric testing modality has become more popular due to the availability of testing products.
The first generation of such isometric testing devices were developed in the early 1980s and involved measurement of only the maximal force using a cable tension meter or dial gauge. The disadvantages of these systems include the ability to measure only gross large forces, poor sensitivity at small forces, and an inability to dynamically measure forces. Additionally, the cable systems were cumbersome, setup times were long, and the number of muscle groups that could be tested was severely limited.
The second generation of these isometric testing devices use computerized testing platforms with a chair utilized for upper and lower extremity bilateral testing, spine evaluations, and lifting assessments. These systems analyze the force curve over time, provide feedback on cogwheeling, measure fatigue, determine rate of contraction, assess consistency of effort, calculate averages, determine bilateral deficit, etc., all relating to the performance of a patient.
One disadvantage of these above-described devices is the nonintegrated test chair. The chairs included in these devices were added as an afterthought. The chairs use considerable floor space due to their size, are heavy, and must be wheeled or carried into place over the platform for use. In addition, the patient must be removed from the chair and the chair moved several times during most exams, making the exam longer and more involved.
Thus, there is a need for a device which more conveniently incorporates a chair for spinal, upper, and lower extremity tests, but still conveniently allows for lift and functional testing of a patient without the chair being a hinderence.
Another disadvantage of these above described devices is that the load cell operates in tension only, requiring multiple setups for antagonist/agonist testing. In order to provide assessments of antagonist/agonist muscle groups, cumbersome cables or straps must be used. After testing the agonists, the patient and chair must be turned around to keep the load cell in tension to test the antagonists, which increases the setup and documentation time considerably. For example, when measuring the biceps, the handle, cable, and transducer are pulled to place them in tension. When measuring the opposite motion (elbow extension using the triceps), however, the patient and chair are turned around to keep the cable/strap in tension. This requires two different setups for the chair and patient. In addition, moving in and out of the chair for every test may prove even more time consuming, burdensome, and painful for injured patients.
Thus, there is a need for a device with a load cell that operates in both tension and compression so that agonist/antagonist muscle assessments may be completed in a single patient position.
Another disadvantage with these above described devices is that they use two-dimensional positioning to orient the load cell with respect to the muscle group being tested, requiring complex bilateral testing setups. The positioning methods of most systems include adjustment of the load cell height, load cell angle in the vertical plane, horizontal distance from the load cell acting point, chair orientation, etc. But in most systems, the direct line of action between the plane of movement of the muscles being tested and the centerline of the transducer results in large errors in maximal force. For example, during a knee flexion test, the patient is seated in a chair and a strap is connected around the leg just above the ankle. The tranducer is lowered so the strap is horizontal. With the patient seated in front of the transducer, the line of action is 24 degrees resulting in a strength measurement error of approximately 10 percent.
Thus, there is a need for a device which provides for more convenient and accurate bilateral testing. In order to solve this problem, some devices move the chair, and the patient, to the right for left side testing and to the left for right side testing. This cumbersome procedure equalizes the line of action for the muscles being tested and the tranducer, but the patient is requires to exit the chair, the chair is moved, and the patient is then repositioned on the chair. If multiple tests are required, the problem is compounded. Thus, there is still a need for a more convenient device for bilateral testing. In addition, there is a need for a device that provides a direct line of action between the transducer and the point line of action.
Another disadvantage of the prior art devices is the decreased repeatability of the tests due to the use of cables and straps. The use of cables and straps makes it difficult to position the patient exactly the same for follow-up tests. Thus, there is a need for a device that eliminates straps and cables to improve the repeatability of follow-up tests.
Another disadvantage in some devices is the requirement for two testing systems, one with a chair for testing the extremities and another with a platform for lift testing. Two devices require additional floor space and expense. Thus, there is a need for a device that requires less floor space and reduces expense but which can perform various different isometric tests on a patient.
An additional disadvantage of the above described devices is that they are unable to meet clinical requirements for functional diagnostic testing or post offer employee testing. Functional diagnostic testing in clinical environments requires a device that may be quickly customized for testing. Post offer employee testing requires objective, baseline, tester independent, easy to administer, standard and job specific isometric strength tests. Current devices were not designed for these emerging uses. Thus, there is still a need for a device that can be quickly customized for different tests and provide objective and easily administered tests.
In view of the above mentioned disadvantages, it would be an advance in the industry to provide an apparatus for isometric testing which overcomes these and other drawbacks.